The present invention relates to a method for the preparation of an organosiloxane oligomer and a novel organosiloxane oligomer prepared by the method. More particularly, the invention relates to a method for the preparation of an organosiloxane oligomer represented by the general formula EQU YSi(R.sup.1).sub.n (--O--SiR.sub.3).sub.3-n,
in which each of the groups denoted by R and R.sup.1 is, independently from the others, a halogen-substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, Y is a monovalent atom or group selected from the class consisting of a hydrogen atom, methyl group, phenyl group, vinyl group, chloromethyl group, 3-methacryloxypropyl group and 3-acryloxypropyl group and n is zero, 1 or 2. Among such organosiloxane oligomers, in particular, those expressed by the general formula EQU Y.sup.1 Si[--O--Si(CH.sub.3).sub.2 (CH.sub.2 CH.sub.2 CF.sub.3)].sub.3,
in which Y.sup.1 is a hydrogen atom, chloromethyl group or 3-methacryloxpropyl group, are novel organosilicon compounds not known in the prior art or not described in any literatures.
As is known, recent progress in the modern high technologies requires supply of various novel materials having high performance and organopolysiloxane or so-called silicone products are also not outside this current. In order to obtain a novel silicone product of high performance, one of the basically important conditions is to develop a variety of intermediate compounds or organosiloxane oligomers such as those represented by the general formula YSi(R.sup.1).sub.n (--O--SiR.sub.3).sub.3-n, in which each symbol has the meaning defined above. The organosiloxane oligomers represented by this general formula of course include those relatively simple organopolysiloxane compounds which can be prepared by a known prior art method without particular problems. When a specific organosiloxane oligomer useful in a specific application is desired, however, no prior art method is known which is generally applicable to the preparation of various kinds of such organo-siloxane oligomers so that it is very important to develop such a method having versatility. In particular, no industrially advantageous method is known for the preparation of an organosiloxane oligomer having an unsymmetrical molecular structure such as 1,1,3,3-tetramethyl-3-vinyl disiloxane, which, in the prior art method, is prepared by the cohydrolysis-cocondensation reaction of dimethyl chlorosilane and dimethyl vinyl chloro-silane only in a low yield.